Fitxer:Crystalline placer gold (derived from a conglomeratic paleoplacer in Uairen Formation, Paleoproterozoic, about 1.7-1.8 Ga; Santa Elena Placer Gold District, southeastern Bolivar State, southeastern Venezuela) 2 (15120809111).jpg
Crystalline_placer_gold_(derived_from_a_conglomeratic_paleoplacer_in_Uairen_Formation,_Paleoproterozoic,_about_1.7-1.8_Ga;_Santa_Elena_Placer_Gold_District,_southeastern_Bolivar_State,_southeastern_Venezuela)_2_(15120809111).jpg (514 × 481 píxels, mida del fitxer: 246 Ko, tipus MIME: image/jpeg)
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Resum
| Descripció |
Crystalline placer gold (skeletal octahedral crystal; hopper octahedral crystal) (5.5 mm across) from the Santa Elena Placer Gold District of Venezuela. Gold nuggets found in rivers & streams (= placer gold) usually have irregular, somewhat rounded shapes. It’s rare to find placer gold having a crystalline structure. Here’s the top and bottom of a nice gold crystal from Venezuela’s Santa Elena Placer Gold District. The top of the specimen (see other photo in this album) shows the upper half of an octahedral crystal (a square pyramid). Notice that each of the four faces of the pyramid are embayed. Such features are not uncommon in natural crystals. The terms hopper octahedron or skeletal octahedron would be applicable here. A few grains of sediment are stuck at the bottom of a couple of these cavities. The underside of the sample (this photo) has the typical irregular, dimpled, somewhat rounded shape of many placer gold nuggets. Geologic context: placer gold in modern alluvial deposit; gold is derived from weathering of conglomeratic paleoplacers in the Uairén Formation, Roraima Supergroup, upper Paleoproterozoic, ~1.7-1.8 billion years. Locality: unrecorded locality in the Santa Elena Placer Gold District, near Santa Elena de Uairén, Grand Savannah River region (La Gran Sabana), southeastern Bolivar State, southwestern Guyana Highlands, southeastern Venezuela. |
| Data | |
| Font | Crystalline placer gold (derived from a conglomeratic paleoplacer in Uairen Formation, Paleoproterozoic, about 1.7-1.8 Ga; Santa Elena Placer Gold District, southeastern Bolivar State, southeastern Venezuela) 2 |
| Autor | James St. John |
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This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/15120809111. It was reviewed on 6 d'abril de 2015 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Data/hora | Miniatura | Dimensions | Usuari/a | Comentari | |
|---|---|---|---|---|---|
| actual | 22:35, 6 abr 2015 | | 514 × 481 (246 Ko) | Jacopo Werther | Transferred from Flickr via Flickr2Commons |
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